Refractory material.



i greatas in a fire brick lining.

silicon carbid furnace linings it has there KEANE Ll". TONE, O]? NIAGARA FALLS, NE'W YORK, IaSSIGNOIEtTU THE CAHBORUNIJUM GUMPANY, (Pl? NIAGARA FALLS, NEW YORK, A CORPORATION OF S'ZL'YJANIA.

REFRACTORY MATERIAL.

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To all whom it may concern y Be it known that I, FRANK J. Tonga, resident of Niagara Falls, in the countytof Niagara and State of New York, have invented a new and useful Refractory Material, of which. the following is a full, clear, and exact description.

My invention relates to refractory Inaterials, particularly those used for furnace linings and metallurgical structures; and the object of the invention is to provide a new and desirable form of silicon carbid which will utilize its high refractory power and remove the objection heretofore present, of low resistivity to heat conduction.

The refractory properties of silicon carbid have long been known and ithas had a considerable application as furnace lining both in the form of bricks, rammed, or otherwise applied solid linings. But notwith standing its infusible and refractory nature, its low thermal resistivity has been a great objection to its use especially in certain applications; it being a good conductor of heat as compared with, fire brick. Recent published investigations give a value of 10.3 thermal ohms per cubic centimeter for the resistivity of silicon'carbid brick at 1000 CL and a value of 5'? thermal ohms for ordinary fire brick at the same temperature.

The conduction losses in, a silicon carbid lining would therefore be over five times as In using fore been proposed to prevent the loss of heat by suitable insulating material. But this combination has presented difficulties because silicon car-bid linings have their chief application where temperature or other conditionsare most extreme and where many of the well known insulating materials such as asbestos, or silicon monorid, undergo a change at high temperatures and lose much of their insulating value. I have found that I can overcome this difliculty by forming a linin in which the working portion, exposed to high temperature and requiring stability and strength, is formed of silicon carbid of high refractability and low ther mal resistivity; and by backlng up this'layer with silicon. carbide of a form which, although lacking in strength and refractability as compared with the other portion, has very high thermal resistivity. For the Specification of Letters Patent.

racemes new. ii, mas.

Application filed April 263, 1912. Serial ll'o. 693,-l96.

first named exposed or working portion 1 April 15, 1913, entitled Silicon carbid articles and method of making the same, in which porous carbon is subjected at high temperature to silicon-containing vapors and converted into porous silicon carbid of low apparent density and apparently noncrystalline structure. I may also use other materials having the desired properties in which silicon carbid is one of the con.- stituents, for example the material described in my pending application No.

(381,623, filed March 4th, 1912, which. is thought to be a solid solution of s...1con

carbid in silica, and is characterised by logy apparent density and high thermal re sis'tivi lay.

When desired for mechanical or other rea sons, my composite silicon carbid lining may be supported or backed up by orr'linary means such as the steel furnar'se e'l or by walls of less refractory bricks.

The advantages of my invention result from the use of the two grades or species of silicon carbid, namely the dense grade giving the higher infusible and ref actor-y properties combined with a backing of the porous carbid having high thermal resistivity. This combination overcomes the objection to the use of dense silicon carhid as a refractory material and at the same time overcomes the diliiculties in using other backing up materials in high te'uiperatiu'es.

Thetwo' silicon carbid materials may be produced in any desirable Way and by any desirable apparatus. It may be found economical for example for use in certain-refractory structures to produce the two materials in one and the same article in a coin posite form.. In such case the working portion would be composed of the dense silicon carbid with a backing of porous silicon car bid. The article to be silicidiaed would first be formed having its respective portions so constituted that one portion would be suitable for conversion into dense silicon carbid and the other portion suitable for conversion into porous silicon carbid. The article would then be placed in the silicidizing zone of the furnace so that the first portion would be subjected to a temperature suflicient to convert it into dense silicon carbid, and the second portion so placed that it would be subjected to a lower'range of temperature sufiicient only to convertit into porous silicon carbid.

I claim 1. Refractory material, comprising a layer of dense silicon carbid and a layer of porous silicon carbid of relatively high thermal resistivity. i

' 2. Refractory matcriahcompiising a layer of dense silicon carbid, and a contiguous layer of porous silicon carbid of low apparent density and high thermal resistivity.

3. A refractory structure consisting of a layer of silicon carbid of high refractahility and mechanical strength, and of low thermal resistivity, and a contiguous layer of silicon caihid of porous structure, low apparent In testimony whereof, I have hereunto set my hand.

FRANK J. TONE.

Witnesses:

EARLE H. FINNEGAN, J. Barnes. 

